Removable hard disk drives are sometimes grouped together into a larger unit or array, such as in Redundant Arrays of Inexpensive Disks (commonly referred to as "RAID systems"). A cast rack with guide rails generally houses the array of hard disk drives. Typical racks may house six rows of disk drives, and each row may contain eight drives arranged horizontally. Each disk drive in the rack is housed in a plastic drive carrier that slides into the rack along a guide rail. Each drive carrier is typically constructed of two substantially symmetrical halves or pieces, each of which has a number of air channel openings. The pieces are fastened together around grooved symmetrical guides.
Unfortunately, these systems face a serious problem with vibration which is a significant cause of disk drive failure. Each hard drive contains a rotating spindle which generates vibrations. The vibrations are not fully absorbed by the carrier. In addition, the construction of the carrier precludes fixing the drive in a manner that eliminates vibration. Furthermore, it is not economically feasible to construct the disk carriers in such a way that they fit together in the cast racks with tolerances tight enough to eliminate the vibration of the carrier within the rack.
Five and a quarter inch disk drives which were previously in use tolerated the vibration well, in part because the higher form factors had lower track and bit densities. However, with the movement towards miniaturization, such as in three and a half inch disk drives, the smaller form factors have higher bit and track densities and are extremely susceptible to vibration. With smaller drives presently in use even slight vibrations cause read and write errors, and substantial vibration(s) may cause disk drive failure.
One implementation aimed at addressing the vibration problem involved compressing a strip of Velcro.RTM. between the drive carrier and rack structure. Velcro.RTM. is a compressible material that slides with relative ease along the guide rail. This method of dampening vibrations poses several problems. Because it is difficult to fix the Velcro.RTM. to the drive carrier, the Velcro.RTM. has a tendency to slip out of place as the drive is slid relative to the rack structure. The Velcro.RTM. also makes it more difficult for the drive to be inserted because engagement channels on the drive carrier cannot fully engage the guide rail with the Velcro.RTM. in place. Furthermore, the Velcro.RTM. compresses after a period of time thereby reducing the vibration dampening properties resulting from disposing the compressible material between the drive carriers and the rack structure.